Electric machines play an integral part of systems in a variety of industries. In applications such as electric vehicles and starter-generators, machines are driven into saturation to meet high torque demands while optimizing for cost and weight. Therefore, the electric machine parameters can vary substantially during normal operation. When developing controls, machine parameters are often used to tune the controller gains. As a machine is driven into saturation, the controller gains may need to be modified online to correctly compensate for the change in machine parameters. If not correctly compensated, the controller may become unstable. Further, control strategies such as Maximum Torque per Ampere are impossible to implement without considering saturation effects in the control algorithm.
In this study, flux-based PMSM models incorporating saturation using analytical functions and look-up tables are discussed. Further, simulation results of a machine with heavy cross-saturation modeled based on an analytical function and look-up tables are shown. The PLECS models for the PMSM with heavy cross-saturation and corresponding application note are available for download below. Additionally, a model of a PMSM with low cross-saturation is provided.
Above is a MATLAB-based rendering of of how machine saturation information available from FEA studies or measurement data can be formatted for use within a PLECS simulation. In this case raw FEA data for a machine with high cross-saturation effects is shown with dots, and the surface data is generated and made available for PLECS using look-up tables.
- PLECS Blockset 3.7 or newer
- MATLAB 7.5 (R2007b) newer
- PLECS Standalone 3.7 or newer
The application note in PDF format, as well as the corresponding models for PLECS Blockset and Standalone, data files, scripts and supporting documentation can be downloaded here.